*"" -282 PRACTICAL ORGANIC CHEMISTRY
The product can, however, be converted into the mustard, oil
by treatment with a metallic salt which removes hydrogen
SC< " " - HoS + NIIo.CoII, + SC:NC,HB.
Among the reactions appended to this preparation, the for-
mation of phenylcarbimide from phenyl mustard oil is described.
It should be noted that phenyl carbimide, like the thiocarbimicle,
unites with ammonia, amines, and more especially with alcohols
and phenols. The bases yield urea derivatives ; the alcohols
and phenols form urethanes.
C«H5N:CO + NH;) = CBHSNII.CO.NH3 Phenyl urea.
CflHfiN:CO + NH3CHS = C6HBNH.CO.NHCH3 Methyl phenyl urea.
Ct;H5N:CO + CJI5OH = C(iH5NlI.CO.OC2H5 Phenyl urethanc
Q;II5N:CO + CGH5OH = C0IIBNH.CO.OC6H0 Phenyl carbamic
The latter two reactions are frequently used for detecting
the presence of a hydroxyl group (Goldschmidt).
Diazobenzene Sulphate. — Whereas nitrous acid imme-
diately decomposes the primary aliphatic amines with evolution
CH3NH2 + HN0.2 = CII.OH + N2 + H2O,
no nitrogen is evolved if nitrous acid is allowed to act upon a
salt of a primary aromatic amine in the cold. The solution then
contains a diazo-salt, which is readily soluble in water. It may
already have been observed that in the salts of diazobem-
ene, the radical, diazobenzene, Cf>Hf,N2, plays the part of am-
monium, NH4, in the ammonium salts. Diazobenzene chloride,
nitrate, sulphate, &c., correspond to ammonium chloride, nitrate,
C6H,N2. SOJi NH4. S04H.
The hydrate of diazobenzene, C6H5N2.OH, which would be
analogous to NH4OH, is also known as an unstable oil. Con-